Cataclysm Leaves Wealth of Minerals

That complex geological history has left the region with a wealth of minerals, many of them formed when the rocks in these desert ranges were deep beneath the ocean along the crack in the Earth between two crustal plates. The weak crust along such gigantic fissures lets molten rock from the deep Earth escape to the surface, as it does now along undersea ridges like the Mid-Atlantic Ridge, which is recognized as the greatest mountain chain on Earth. As magma and superheated water percolates through such fractures in the crust, the heat and pressure spur chemical reactions that cause a variety of minerals to form in the fissures. So the gold, copper, silver, iron, lithium, beryllium, molybdenum, and barite that have drawn miners to the Great Basin Desert for more than a century all bear witness to the complex and violent geological history of the rocks that comprise its mountains.

For most of its history, the Great Basin Desert was a grassland graced by vast lakes that supported thriving populations of hunters and gathers, stalking great herds of antelope, camels, and even mammoths. Some 12,000 years ago during the last Ice Age, places like the now-desolate Carson Sink harbored huge lakes. Flush with more than 18 inches of rainfall a year during that long cold snap in the planet's climate, the once year-round Humboldt River flowed into Lake Lahontan, which flooded most of central and northwestern Nevada. It covered 9,000 square miles (2,330 sq km) and had a high-water mark of 4,378 feet (1,459 m) above sea level.

As the climate warmed and the river withered, it became a fitful and capricious drainage system that mostly vanished into thirsty sands and salt flats. Mark Twain observed that “one of the pleasantest and most invigorating exercises one can contrive is to run and jump across the Humboldt River till he is overheated, and then drink it dry.”

The once-mighty Lake Bonneville in Utah formed an even more impressive body of water during those wet, lush times. Trapped in an interior basin, the lake gradually filled up, reaching a high-water mark roughly 14,000 years ago. At that point, it rose above a natural dam of rock at Red Rock Pass in southern Idaho and rushed down to the Snake River. It spawned a flood of biblical proportions. The lake fell 10 feet (3.3 m) in four days. In six weeks, the lake level fell 350 feet (117 m), causing a massive flood rushing down into the Snake River, whose traces remain vivid and jumbled all along that path. The lake stabilized at about 4,800 feet (1,600 m) above sea level for the next 6,000 years, before climate shift gradually dried it up.

The Great Salt Lake is another remnant of the Ice Age. As it evaporated, it left behind salts and minerals. That resulted in the Bonneville Salt Flats, a place so hard packed and flat with crystallized salts that rocket-powered race cars now use it to set land speed records. The Great Basin didn't actually become a desert until after the ancient lake vanished and the climate warmed, which means the plants and animals have perfected their elaborate adaptations to a desert environment in the past 6,000 to 10,000 years.